This invention relates generally to inspecting a pipeline for anomalies, and more specifically to inspecting a pipeline using a reflected component of an input waveform.
To maintain substantial fluid flow through a pipeline, internal pipeline characteristics need to be monitored so that defects, obstructions, and other anomalies in the pipeline can be detected and repaired efficiently. In addition to obstructions affecting fluid flow in the pipeline, a pipeline may bend and/or buckle when it experiences a change in pressure, such as when the pipeline is laid underwater. Frequently, companies must endure substantial monetary costs and schedule delays due to the detection and repair of these pipeline anomalies.
In some conventional systems, an internal, invasive device that crawls the length of the pipeline is used to inspect a pipeline for anomalies. This device, often called a xe2x80x9cpigxe2x80x9d, poses a serious blockage to the normal fluid flow through the pipeline. A pig may additionally require several days for the inspection of a lengthy pipeline. Furthermore, the amount of data a pig can record, the life of its battery, and the wear of its components from crawling the pipeline all limit the usefulness of the pig.
Measuring the acoustic signature of a pipeline is another technique used to detect pipeline anomalies. This technique sometimes involves hitting the pipeline on its side with a hard object, such as a hammer, and then measuring the acoustic signature of the pipeline. Anomalies often alter the acoustic signature of a pipeline as compared to a pipeline with no such anomalies. However, the magnitude of the anomaly that may be detected is dependent upon the wavelength of the waveform transmitted along the pipeline, and sound waves generally have longer wavelengths than some other waveforms. Therefore, this technique typically fails to detect smaller-sized anomalies in a pipeline.
Pulse propagation may also be used to detect pipeline anomalies. According to one technique, two pulses are transmitted along the pipeline from opposing locations towards an intersecting location. The pulses intersect and are each modified by collision with the oppositely directed pulse. A receiver is positioned at the intersecting location and, after receiving the modified pulses, analyzes at least one indicator characteristic of one of the modified pulses to determine whether an anomaly exists between the receiver and the corresponding transmitter. However, this technique usually requires two separate transmitters and a separate receiver, each of which increases the costs associated with detecting anomalies. Also, pulse propagation analysis may further require inserting the receiver into a location in the pipeline not normally open for device placement.
Another conventional approach is an ultrasonic guided wave inspection technique that uses stress waves, such as Lamb waves. Since Lamb waves are typically guided along the pipeline, lateral spreading of the energy associated with these waves does not usually occur and the propagation is essentially one-dimensional. For this reason, Lamb waves normally propagate over longer distances than other types of waves, such as bulk waves. Unfortunately, at least two modes typically exist at any frequency for Lamb waves. Furthermore, the modes are generally dispersive, which means that the shape of the propagating waveform varies with distance along the pipeline. Consequently, interpretation of the signals is difficult and can also lead to signal-to-noise problems.
Accordingly, it is desirable to produce a system that is capable of detecting an internal characteristic of a pipeline in a non-invasive fashion. It is also desirable to be able to inspect a pipeline faster than currently possible, as well as to be able to accurately detect smaller-sized anomalies in a pipeline.
Briefly, the invention relates to a system and method for inspecting a pipeline. In one embodiment, the invention provides a system for detecting and characterizing an anomaly in a pipeline. In another embodiment, the invention provides a system that can also determine the longitudinal path/shape of the pipeline. With a starting point and the longitudinal shape of the pipeline, a further embodiment of the invention can also determine the location of a pipeline buried underground or even under water. According to one preferred embodiment, the system includes a processor, an analyzer, and a wave launcher. In an alternate embodiment, the analyzer, wave launcher, and processor are incorporated into a single unit, thereby eliminating the external connections between the devices. The wave launcher communicates with the pipeline, and is adapted to transmit an input waveform having a selected input energy along the central longitudinal axis of the pipeline. Examples of the type of input waveform include, but are not limited to, an electromagnetic waveform, a wideband waveform, and an acoustic waveform. Further examples of input wideband waveforms include, but are not limited to, a chirp waveform, a spread spectrum waveform, a wavelet waveform, and a solitons waveform. The wave launcher is further adapted to receive a reflected component of the input waveform having a characteristic reflected energy. An example of the wave launcher includes an antenna adapted to transmit the input waveform along the pipeline.
The analyzer communicates with the wave launcher, and is adapted to generate the input waveform. The analyzer is further adapted to receive the reflected component of the input waveform from the wave launcher. According to a further feature, the analyzer includes a signal generator, energy component devices, and a directional coupler. The signal generator generates the input waveform that is transmitted along the pipeline. The energy component devices extract out the magnitude and phase components of the input energy and the reflected energy associated with the input waveform and the reflected component of the input waveform. An example of the analyzer includes an automated vector network analyzer.
According to one embodiment, the processor communicates with the analyzer, and is adapted to compare the input waveform with the reflected component of the input waveform to generate a mathematical model for the pipeline. According to one feature, the mathematical model includes information regarding the longitudinal path/shape of the pipeline. According to another embodiment, the processor and the analyzer interact to detect and determine the characteristics of an anomaly in the pipeline. Examples of an anomaly in the pipeline include, but are not limited to, an obstruction, a flange, rust, and poorly constructed welds. Specifically, the characteristics of the anomaly include, but are not limited to, the location of the anomaly in the pipeline, the type of anomaly, and the size of the anomaly. According to a further feature, the system of the invention displays the characteristics of the anomaly and/or the shape/location of the pipeline to a user.
In one operational embodiment, the processor initializes the analyzer. Optionally, the processor initializes the analyzer by calibrating it. Illustratively, the processor calibrates the analyzer by temperature stabilizing the analyzer. In one embodiment, once the processor calibrates the analyzer for operation, the user of the inspection system of the invention inputs the diameter of the pipeline into the processor. The processor uses the diameter to determine the frequency range at which the input waveform can propagate along the central longitudinal axis of the pipeline. The processor transmits this frequency range to the analyzer and the analyzer generates the input waveform having a frequency within this range. The analyzer transmits the input waveform to the wave launcher, and the wave launcher launches the input waveform along the central longitudinal axis of the pipeline.
In a further embodiment, the analyzer extracts the input energy associated with the input waveform. When the analyzer receives the reflected component of the input waveform, the analyzer extracts the reflected energy associated with the reflected component. According to another feature, the analyzer then determines a mathematical representation, or transfer function, relating the input energy and reflected energy. The analyzer then transmits this information to the processor.
In one embodiment, the processor determines the energy reflected from the obstruction by generating a mathematical model of the inspection system of the invention and the pipeline. According to this feature, the processor determines a model transfer function relating the input energy of a model input waveform and the model reflected energy associated with a model reflected component. In one embodiment, the processor determines the characteristics of the obstruction from the model transfer function and the transfer function for the input waveform. In some embodiments, the processor determines which mathematical model to use from the transfer function relating the input energy and reflected energy. The processor can use, for example, an ideal physics-based model, an average model, and/or a section-by-section model to model the pipeline.
According to a further feature, the processor displays the characteristics of the anomaly with a textual representation on an output device. Alternatively, the processor displays the characteristics with a graphical user interface, a three-dimensional solids rendering plot, or an echo plot.
In some embodiments of the invention, the pipeline curves along a longitudinal central axis. In one aspect, the user of the inspection system still provides the diameter of the pipeline. Using the diameter, the processor determines a different range of frequencies at which the input waveform can propagate to aid the processor to model the curved pipeline accurately. Once the processor models the curved pipeline accurately, the processor determines the shape of the pipeline, the location of the pipeline, or the characteristics of the obstruction.